Most people have heard of the MP3 format. It’s an example of two things: First, it is not an open format, as a number of organizations claim patents on it. And second, it is a “lossy” format. Lossy formats compress the original signal by throwing out some of the signal components. The original rationale for this compression was to make music files smaller and more easily distributed. In contrast, there are also “lossless” formats, which can be compressed (without throwing away the original signal) or not. Digital music presented on the Compact Disc (CD) is an example of a lossless format (assuming it’s an audio CD, not a data CD with MP3s saved on it).